The invention relates to a rotation piston internal combustion engine with a rotor which rotates at uniform velocity within a stationary cylindrical housing, with at least four ribs essentially directed radially inward from a cylindrical outside wall of the rotor, with a hub rotating concentrically to the rotor inside the rotor, at non-uniform velocity, with at least four pistons projecting radially beyond the hub at equal radial angles from one another, engaging with the interstice between each of two ribs, and performing an oscillation motion relative to these, with at least four crankshafts which pass through the ribs of the rotor axially and can be put into rotary motion by the oscillation motion of the pistons, by means of connecting rods, and with gear wheels arranged on the crankshafts so as not to rotate, which mesh with a ring gear which has gear teeth on the inside and is elastically connected with the housing.
A rotation piston internal combustion engine of this type is known (EP-A-00351136), in which a light and compact construction is ensured in that the crankshafts are passed through the ribs of the rotor. To avoid unbalanced conditions, the crankshafts have to be arranged point-symmetrically to the axis of rotation of the rotor, so that for an engine with four pistons, four crankshafts also have to be provided. Here, the crankshafts are mounted in friction bearings within the rotor. Therefore, very little play is left available at the crankshafts to balance out dimensional deviations in the production and assembly of the connecting rods. If the dimensional deviations are greater than the available play in the case of one or more connecting rods, this results in irregular stress on the connecting rods and, therefore, an out-of-round movement of the gear wheels, which can result in the risk of gear tooth damage, especially at high engine output and high speeds of rotation. In order to avoid this, the stresses are absorbed by an elastic element arranged between the ring gear and the housing mantle. In the known rotation piston internal combustion engines, sleeves inserted in frontal end bores of the ring gear to hold bolts which engage with adjacent bores of the housing cover with their ends that project beyond the ring gear, are used as an elastic element. Studies have shown, however, that the elastic sleeves are not able to withstand the stresses of engine operation, particularly at high engine output and high speeds of rotation. The damage to the sleeves which occurs in this connection is primarily attributable to excessive surface pressure. Causes for this were determined to be the shock-like stresses which occur during the movement of the four gear wheels, on the one hand, and a difference in thermal expansion of the housing cover and the ring gear, on the other hand. The difference in thermal expansion results in constant compression of the sleeves in the radial direction during operation, with the tangential, shock-like stresses being superimposed on them. The invention is based on the task of improving the known rotation piston internal combustion engine of the type stated initially in such a way that the reciprocal stresses which occur between the ring gear and the housing cover can be permanently absorbed.
To accomplish this task, it is proposed, according to a first alternative of the invention, that the parts of the connector bolts which engage with the blind holes of the housing cover are provided with a coating of rubber elastic material, and the parts of the connector bolts which project beyond the housing cover engage with the frontal end bores of the ring gear with a tight fit. With this measure, what is achieved is that the stresses which result from the static redundancies in the case of more than three connecting rods can be permanently absorbed by the rubber elastic coating on the parts of the connector bolts which engage with the blind holes of the housing cover. A further improvement in this regard is achieved if the parts of the cylindrically formed connector bolts which engage with the blind holes of the housing cover have a greater diameter than the parts which engage with the bores of the ring gear. The rubber elastic coating should lie close against the wall and the base of the blind hole in question in the unstressed state. It is advantageous if the rubber elastic coating is connected with the connector bolts in such a manner that it cannot be removed, preferably vulcanized onto them.
In order to furthermore be able to reduce the stresses which are attributable to the surface pressures resulting from the difference in thermal expansion of the ring gear and the housing cover, it is proposed, according to a preferred structure of the invention, that the hole circle diameter of the blind holes in the housing cover, which preferably consists of light metal, is smaller than the hole circle diameter of the bores in the ring gear, which is made of hardened steel. It is practical if the diameters of the hole circles are selected in such a manner that they are essentially the same at operating temperature.
A second solution variation of the invention provides that at least one damping layer of rubber elastic material, provided between surfaces of the ring gear and a housing cover which lie opposite one another leaving a gap, bridges the gap and connects the ring gear with the housing cover. Advantageously, the surfaces which lie opposite one another and are connected with one another by the damping layer form a circumference or surface gearing between the ring gear and the housing cover. The damping layer can either be composed of parts arranged in pieces at a distance from one another, or be formed as a connected layer which extends over the entire gap length or the gap circumference. Advantageously, the damping layer is vulcanized in between the surfaces of the ring gear and the housing cover which lie opposite one another.
Pursuant to a further advantageous structure of the invention, the ring gear is secured against axial displacement by means of a locking ring, preferably structured as an open spring ring, arranged in a circumferential inside groove of the housing. In this case, it is practical if the inside groove demonstrates twice the width of the locking ring.